Supercharger questions

[Razkal]

one of my dad's friens said he was sourcing a supercharger for his car and i decided to call down one for our '84 laser here.....thing is i don't kno much about that type of forced induction.....like the engine we have is ported and the head shaved....twin carbs....reground camshaft....and new valves......will i still be able to use the supercharger?.....i realize that bein forced induction a slight lower compression will be favorable...but the piston's compresion is stock.....any info at all on using installing and pros and cons wid MY setup is appreciated fellas.. .......

[TeamH2O]

bracket will be needed bolt up the superchrger as it uses the engines belt to spin the pulley, i think they use intercooler as well, so like turbo is same thing, just turbo is off exhaust air and supercharger running on a pulley.....thas all i no about them

[cheese pie]

superchargers have less lag than turbo chargers but dont run as high boost
good for serious low end torque ( the kind to leave some serious rubber on the road ) if is over 4 psi you should run an intercooler , same thign like ah turbo basically except the supercharger runs off a belt , like how ur air conditioner runs off a belt
the air comming in will blow through the carb , bigger jets may be needed or another carb
and you may also need to buy an electric fuel pump , in line kind , these relatively cheep
check these links to learn more about superchargers

http://auto.howstuffworks.com/question122.htm
http://www.speedmodules.com/forcedinduction

[Razkal]

yeah i cjecked the first link cheese...thanx for the second one tho....i would really need an IC if its over 4psi?...i mean seein as its usin atmospheric air and not engine gasses the air charge should be cooler right?....but i guess a lil more research is needed.....i'm gettin the setup at a really good price...so even if it doesnt go in the car i takin it .thanx tho

[TeamH2O]

supercharger decent, if yuh eh planning on running hardcore, they work good i fine

[belalegosi]

yeah i cjecked the first link cheese...thanx for the second one tho....i would really need an IC if its over 4psi?...i mean seein as its usin atmospheric air and not engine gasses the air charge should be cooler right?....but i guess a lil more research is needed.....i'm gettin the setup at a really good price...so even if it doesnt go in the car i takin it .thanx tho

razkal i dont think the exhaust gases used in a turbo setup affects the temp of the air it pumpin. Unless i'm mistaken, the exhaust gases propel a turbine in a next chamber in the turbo and that turbine is connected to another one in another chamber which does actually pump the air in.
Well thats how i think the turbo works

[Hook]

Razkal, once we talkin about compressing the air and blowing it into ur TB, we talkin an increase in the temperature of that air..doesn't matter if it's by TC or SC...u'll need an intercooler

the cool thing is that, since SC boost levels doh usually run too high, a top-mounted IC cud work once u have the clearance above the engine...it'll save u some time, $ and effort rather than installing a front-mounted IC

[R. Mutt]

razkal i dont think the exhaust gases used in a turbo setup affects the temp of the air it pumpin. Unless i'm mistaken, the exhaust gases propel a turbine in a next chamber in the turbo and that turbine is connected to another one in another chamber which does actually pump the air in.
Well thats how i think the turbo works

We are talking superchargers....they are belt driven....not from exaust pressure as with a turbo. Also turbo setup's do effect the intake temperature. Remember as you increase boost you are increasing the turbine portion of the turbo is going to get alot hotter from the larger volume of exaust which flows into it. This increase of heat will effect the ambient temperautre under the hood and thus intake temp. from the compressor's inlet.

Hook is right...an increase of pressure under constant volume results in an increase in temperature.....ie more you increase boost....the hotter the intake temperature....however as far as talk about an intercooler for anoything beyond 4psi...I dunno....I would say more like abve 7psi.....four is really low boost. I cannot show proof to validate this only that large engine like V8's only run intercoolers with such low boost becuase of the high underhood temperature. With smaller four cylinders you should be able to run slightly higher boost levels. Most bolt on kits for 4 bangers utilize between 4-11psi without the use of an intercooler...7psi should be safe without an intercooler...but it's always better to have one anyway for the low intake temp. and added hp as a result.

[X2]

Yeah, turbo's will get radiated heat from the exhaust housing that will heat the air going thru the compressor.. .this adds to the increased temps of the compressing of the air.

4psi of boost is super low and goes almost unnoticed on some engines. An intercooler should go at at anything over 6 psi IMO... running w/o one is not the best idea at all. Most bolt on turbo kits for 4 bangers come w/o intercoolers only because they sell more w/o them. Cost is a major factor since new i/c's cost $500+ (USD) They could care less if you blow your shift up... that's what disclaimers are for.

Superchargers are belt driven by the crank pulley... hence they use some torque to operate... if your engine is weak down low... a supercharger may not be your best bet. Although they have slightly better performance down low as compared to a turbo, they will sap some power to do so and bolting one to a small, lower power engine may not be the best bet. Some people say s/c's can't make high boost... not true... it's all up to pulley diameter. Superchargers can go as high as 20psi with the right pulley. But for your app Razkal... a turbo would be a better route. The manifold fabrication will be easier, so will the piping...especially w/ twin carbs ( I assume).

Dowsides ? Superchargers won't make max boost till the top of your rpm band... whilst a turbo will be on full boil by 3-4k rpm.... where the s/c is still wheezing to pass 4-5 psi. on it's climb to max boost. Turbos also typically are easier to fit to intercoolers... less complex piping. Also, forget boost levels... superchargers historically (for small displacment engines) don't have the best flow numbers... so you might not get the $$ for $$ performance of a fairly large, high flowing turbo. If you match turbo size properly, you can easily match the low end power production of a supercharger.

[Bezman]

razkal i dont think the exhaust gases used in a turbo setup affects the temp of the air it pumpin

breds i have some burns here i got from my turbo when fixing manifold to show you.

i think it is a great idea 4-5psi will make allot of difference.... no need for an intercooller @ 4-5psi (this will also reduce pressure drop), fabricate and aluminium intake plenum, no exhaust manifold needs to be made, no mods to the engine.. just tune - adding fuel and pulling some ignition (If needed)

you will need the obvious belt and mounting brackets, also thinkk about how the intake will be run and most of all, if you have carbs, you need to make in intake plenum (intake box) to put the velocity stacks or as trini's call them "trumpets", of the drafts in.. so the compressed air from the SC will go into the drafts and fuel mixed etc...

that will be your biggest hurdle.. then you got to think about increasing fuel and controilling it, FPR?, also maybe retarding your ignition a bit... (maybe add a better coil & ignition system from MSD or something too)

you should really get everything installed and working and get some one with a widebad 02 sensor "EUGO" and take it on the dyno and tune those carbs and ignition.. to get the right AF mixture. maybe a rising rate FPR?? not too sure about Carb/boosted set ups..

but if it takes a max of 10hp to drive the SC and at 5psi it makes 40hp you net 30hp from this mod. then you can add headers, CAI, ignitiion mods, more radical cam etc... play with pully sizes etc..

turbocharging a Carburetted car can get tricky.. exhaust manifold needs to be made, the intake plenum, intercooler for sure cause of heat soak in the turbo heating the air, still ahve the issues of fuel and timing, and unless you are planning on turning up the boost, then you need to start thinking about CR's and headgaskets etc....

[Bezman]

a good SC to look at is the ones form the Toyota Super Saloons and even the MR2's those are small and VERY Zippy...


a nice carb'd, throaty, fast sharp sounding laser would be cool

i always wanted to do a 92-95 HB civic with a B18, 48mm ITB's (Individual Throttle Bodies), 370cc injectors, MSD 6AL and a 5-7psi SuperCharger for about 240whp,

response and an orchestra of induction and mechanical injection.

[X2]

breds i have some burns here i got from my turbo when fixing manifold to show you.

I once burnt the pattern of a bolt into my thumb when I touched the turbo manifold after starting the car from dead cold and letting it idle for 3 mins !! ouch...

turbocharging a Carburetted car can get tricky.. exhaust manifold needs to be made, the intake plenum, intercooler for sure cause of heat soak in the turbo heating the air, still ahve the issues of fuel and timing, and unless you are planning on turning up the boost, then you need to start thinking about CR's and headgaskets etc....

You said you need a new intake when going turbo ? How come ? (I'm not up on turboing a carb'd car either)

But you did say you need a new intake plenum for s/c's... making an efficient intake plenum is much harder than a turbo manifold..and you still need to make a bracket for the s/c compressor and find a groove for the belt on the crank pulley or other... so I was wondering why you'd say supercharing would be a better way to go ?

[R. Mutt]

Dowsides ? Superchargers won't make max boost till the top of your rpm band... whilst a turbo will be on full boil by 3-4k rpm.... where the s/c is still wheezing to pass 4-5 psi. on it's climb to max boost. Turbos also typically are easier to fit to intercoolers... less complex piping. Also, forget boost levels... superchargers historically (for small displacment engines) don't have the best flow numbers... so you might not get the $$ for $$ performance of a fairly large, high flowing turbo. If you match turbo size properly, you can easily match the low end power production of a supercharger.

You are somewhat incorrect there X2...remember it all depends on the type of supercharger he plans on running: Roots or Centrifugal.

A centrifugal supercharger, is an air pump driven directly from the crank, injecting air it has ALREADY compressed. It delivers exponentially increasing boost as rpm increases. Some like to think of the centrifugal supercharger and the turbocharger as the same thing except with the compressor wheel turned by different means. You are right about one thing here: The centrifugal does experience lag at the lower end also.

However, the other type: a Roots blower, is a positive displacement air pump driven directly from the crank, injecting air it has NOT compressed. It delivers linearly increasing boost as rpm increases.The great difference of the roots type blower is that it produces high boost at low end rpm, with no significant lag.

The man could also go with a twin-screw supercharger and get the best of both worlds: injecting air it has ALREADY compressed, it delivers linearly increasing boost as rpm increases. The twin screw delivers full boost at low rpm, like the Roots, but also delivers compressed air, like the centrifugal and the turbo. With this compressed air however it would be advisable to run an intercooler.

I'm not bothering to talk about turbochargers becuase you question is concerned with a supercharger for a laser and if you'll need to run an intercooler.

[X2]

Well I didn't mention roots chargers due to their inefficiency... although peak boost is sooner than other designs... particularly since the roots charger has bad thermal characteristics due to the design... not the best idea for the setup he wants and 'no intercooler' had been pushed.... both the roots and twin screw have issues with thermal inefficency and the twin-screw... well... look at the cost... it's not cost effective at all...

The centrifigal charger... like a turbo, has great effiencency... is somewhat cost effective, but gets the crappy low end power and his heavily rpm dependant... but the flow you get is immense compared to the other two... since this is a low displacment app and an intercooler may not be used... wouldn't you rather go with a centrifigal rather than a roots style (twin screw included) ?

Good discussion goin...even tho I am not a s/c fan...

[R. Mutt]

You have a very relevant point....and I too prefer turbocharging over supercharging. However it's always good to explain every angle of a question for the person who raised the point since in the end we are discussing to help him make a decision. I was just explaining that a superchargers can make low boost. In addition to this Razkal just wants to see what different options and the pros and cons of each.
If I was dealing with supercharging in Razkal's situations I would use the roots...however up to now we have no idea what kind of supercharger he is talking about for the order...this should be addressed. If he can get a roots type supercharger to use it will be the best bet for his position. Why? Becuase he will be running low boost settings on his car due to the inherent stock nature of his internals, Razkal will be be more interested in obtaining quick boost rather than linear boost......this is a given. Since this is the case and the laser's engine does not encompass high revving capability right now, it seems most appropriate in terms of superchargers. Furthermore, based on The Gas Laws: Changes in pressure are directly proportional to changes in temperature under constant volume. Hence if the air was being compressed Razkal would need an intercooler to chill this hot pressurized air...again a given. Since a Roots type charger does not compress the air...there is no need for an intercooler, again given that he will be runnin boost levels below 7psi. In any case...levels above that....he will being doing more damage than good...potential for detonation and engine wear (since internals were not designed to handle such power) from a number of potential culprets: heat soak as a result of ambient underhood temperatures. running lean with his stock fuel settings, bursting the belt as superchargers are prone to doing with higher boost levels. His head work should also help complement the supercharger in terms of how quickly the power will be delivered at low rpm....the man will get the low end torque contrasting the top end enhancments he would have noticed from the head work. I too am enjoying this discussion.

[Razkal]

WAYYYYYS!!!..thanx there peeps..esp X2 and CT9A ..thas some good reading and info there pallies.......thing is i don't wanna turbo the car....since it bein my first project (i eh no old man yet..lol..only 18) i wanted to cut my teeth in N/A mods but the Sc is at a verry good price so i din mind tryin it out........iread someone said about turbo'in a carb car tho!...how is this done with relevance to the intake piping??..and feeding the compressed cooled air thru the crabs...yes X2 its a twin carb.....i also have a webber at home i could use if that would be easier with the sc......i'm not sure which type it is yet tho.....the guy hasn't told me..
i'm very interested about the turbo carbs tho...can any one elaborate?....i wouldn't mind setting up a low boost system...since the 1500cc laser single cam engine ..(8valve btw )...has it's limits with N/A mods ...btw jnqaz..i was reffering to the relatively big difference in heat exchange/generation with the sc and turbo...the turbo housing heats the compressed air much more than the compressed air in a SC comes out ......i just sort of ruled out turboing as an option bcoz of our now 'high compression' nature fellas.....an was wondering if sc's NEED low compression environments to work in?......to help u guys help me ..these are my mods so far...-:
reground camshaft
4-2-1 extractors
ported and shaved head
aluminum head gasket
high compression pistons (.2 over..not installed yet waiting on sc to decide still)
some kinda aftermarket valves and valve springs (( ..not sure of make))
twin carbs with 3" CAI setup on factory intake 'pan'
and yes its manual
so 2nrs any more info is appreciated..even if it doesn't work out..thanx alot for ur help and no knowlege was wasted...i learnt alot here .....BTW...SC's r not my preference..i much prefer turbos..lol....i just wawnt more speeeeeed

[R. Mutt]

LOL....we all want more speed horse. Ahh....I find you have real mods there jed...car sounding real nice. You modifications thus far are geared towards N/A performance, with ephasis on head work really helps overall performance. However you see those high compression pistons and the shaved head....that's going to conflict with the supercharger. I have no idea what the stock compression on the engine would have been nor what it will be with the overbore. I searched for an equation to calculate compression ratio but the only one used the volume at BDC divided by the vlume at TDC. If you could find the cylinder volume at these instances you can calculate the compression ratio. One thing I am sure about is that the sc was made to run at a specific boost level taking into account that the compression ratio was that of stock specs. Since you have raises this ratio...you will no doubt be limited to the amount of boost you can run.....infact I wouldn't even go above the recommended setting the sc comes with....else you could damage your engine man. If you knew you were going to be sc from before you should have bought low compression pistons and stonger rods...so I'm guessing you did not have forced induction planned for the future and went with the high-compression.

[Razkal]

^yeah CT9A .....but the pistons not in yet! ..i just recently got 'em so they still in my garage!.....i was waitin on some info an a lil more know how before going ahead bro....our rods are pretty good i think..they're from the 323 of the same year....parts from those cars are interchangable thank god...only think that prob affected compression would be the shaved head right?..(it was shaved as much as possible btw....so a blown head would put my arse in some hot water )......i am also open to any more mods that could be safely done to my DAD'S (lol) car that would increase power along the N/A lines...it also has 2.5" exhaust system...no cat....

[cheese pie]

Razkal, thats sounding like ah great project

[Razkal]

well thanx man..its in really good condition too....an dad uses it now as a daily driver.......lil cream coloured laser wid black 14" steellies....real sleeper..lol.......i could always use a hand wen we doin stuff....an ya'll could maco de 'race car'

..question!---i just thought of this.....can i increase displacement on this engine??....i mean if i knew i was gonaa do all that stuff to it i waould have wanted a more promising platform tho.....but now i'm stucj with a 1500 8valve that i reallly dont wanna swap out (too much hard work went into it man) so can i increase displacement in any way without adverse side effects?

[R. Mutt]

Yeah man...you can increase the displacement...this will also increase the compression ratio so you will not be running any form of forced induction. The high compression is a possibility but you ain't gonne feel much of a difference with that small engine....you will have more fun for now, but get bored. The supercharger sounded like a better plan. Find out your bore and stroke and use the equation below to find your compression ratio and we'll take it from there. The next step will be to discuss with other ford or mazda owners how much boost those pistons and rods can handle.

As far as calculating the compression ratio...hmm. You will need the Bore & Stroke.
The radius will be half the bore and the height at BTC will be the stroke. For the volume at TDC you could use 0.04L or 2.5 cubic inches (as refrenced in an example from Auto Engines Technology by James E. Duffy)....ok so hear is an example:

using equation pi x r^2 x h and taking into account we have a square engine of 76 mm/3 IN. (^2 = squared) H is taken as a constant.

Volume at BDC: 3.14 x (1.5)^2 x 3 = 21.2 cu./in
Volume at TDC: 3.14 x (1.5)^2 x H = 2.5 cu./in

V @ BDC / V @ TDC = 21.2 / 2.5 = 8.48

Therefore our compression ratio is 8.48:1

Now just find out your bore and stroke and if possible the minimum volume at TDC for the laser engine. Don't forget to incorporate the added increase to the bore as part of the radius in your equation. Good luck boostin

[R. Mutt]

I would like some input from other guys on this

[X2]

You will need to CC the head (measure combustion chamber volume) to calculate your compression ratio meng. Knowing bore and stroke with an average combustion chamber volume as per

For the volume at TDC you could use 0.04L or 2.5 cubic inches (as refrenced in an example from Auto Engines Technology by James E. Duffy)....

will give you inaccurate figures (very inaccurate) Since you shaved the head, you reduced combustion chamber volume enough to raise compression notably. You will also need to calculate piston crown volume. Without these figures, you can't calculate accurate CR.

As far as no intercooler... the roots type charger may not heat the air due to compression, but the thermal inefficiency (high intake temps) will still be present due to the increase of friction of the air thru the s/c's lobes. That's why positive displ. s/c's have thermal issues. No intercooler is asking for trouble.

Razkal... why are you not looking into turbo ? Don't listen to those people that s/c engines have 'low maintenance' or being more reliable meng... that is a fallacy, boost is boost... unless the car comes s/c'd from the factory... you will need to watch it closely... whatever form of boost you go with. A small turbo like a t25 or a 14b turbo will spool mega quick and give you that low rpm response you want. But don't listen to me... on small displ. engines, I'm pro turbo all they way....

[R. Mutt]

I ent go lie X2....you real know yur sheit...u be just obsessed with cars or SAE certified? You do your engine work on the evo when you get time? Is blue right?

[X2]

hahaha... funny... I doh have an evo. ... the sarcasm is thick with this one..

SAE doh mean much jed... I've worked w/ SAE certified mechs that don't know shift.... I studied with Honda for a short time... not much... but it was fun.

I just love cars, have alot of shop time and am full of random, useless information.... I'm like a gear-head Jeopardy contestant.

[Razkal]

^^i like u guys thinking man..lol.....i'm like that to a certain extent..random knowlege...especially rotaries tho...but i was avoiding turbo cause i mean the engine kinda crappy as a stock for turboin rite?...bein 8valve and all....and i'll have to get a new unshaved head an stuff.....besides the ever present money factor....i really like the intake setup i designed and it woked really well...wish i had pics tho.. ....but X2 i'm always lookin into turbo's man..lol...just don't kno how much sense that'll make on my engine.....can u or CT9A elaborate on the piping (intake in particular) for a carb turbo setup.....i have twin carbs on it now (and a manifold with a webber also in case that's easier)..i'm really interested in this set up on carbs

[R. Mutt]

horse...I'm not the guy to ask about carbs.......X2, fix your mix. Also...hard luck X2...I really didn't mean to sound sarcastic or cynical......I really thought u ruinnin an evo.

[X2]

...hard luck X2...I really didn't mean to sound sarcastic or cynical......I really thought u ruinnin an evo.

De civic runnin so hard you thought it was an Evo, eh ? Thanks for the compliment...

[X2]

btw... I'm not too up on carbs either... only my first car and my other wagon is carb'd and both of those stayed stock as a rock.

Some pics of the engine bay would help tho... I love to fabricate piping... (no play on words there damnit !)

[R. Mutt]

lol @ I love to fabricate piping